A thought as I was driving home last night. There is a problem with car headlamps that they must be bright enough to illuminate the surroundings, but to achieve this we end up with two point sources that are not just uncomfortable to look at but can be positively dangerous (due to dazzle). If the light sources were distributed over the whole of the front of the car - possible with LEDs - would this be less dazzling for the same illumination? As a comparison, whilst I cannot look at a 100W tungstun bulb I can look at a 100W equivalent flourescent tube quite comfortably (because it is not a point source).

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Andy Millar CEng MIET MCMI

http://www.linkedin.com/in/millarandy

Does this help at all?

http://en.wikipedia.org/wiki/Automotive_lighting

Best regards

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sedgwicknc

And this on pupillary reflex. Wikipedia did not seem to helpful on that, and I found this (but have only scanned and not read it). I think it covers both spectral aspects and subtended angle of the light source. Oh, and it's around 3MB, I think as scanned image (from the 1960s).

http://www.pubmedcentral.nih.g...=1359246&blobtype=pdf

Best regards

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sedgwicknc

Many thanks for the links; I think the latter may have some useful info in it, unfortunately slightly indigestible for a coffee-break thought, but if anyone feels like investigating further I would be fascinated to know what comes out (and hope they remember me when they've made their millions )

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Andy Millar CEng MIET MCMI

http://www.linkedin.com/in/millarandy

Edited: 08 December 2006 at 12:46 PM by amillar

Probably not - or if it is, it's not used - judging by the number of cars with one or both dipped beams set at "dazzle me".

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Andy
EurIng Andrew Houston CEng FIET
PRA, PRI and Volunteer Career Manager Advisor

Edited: 08 December 2006 at 02:57 PM by ahouston

What usually gets you is the side lights and the front fogs on when visibility is about 2000 yards (which is a road traffic offence )

Or one car I noticed behind me one day had dipped headlights that flickered blue just like candle bulbs (mmmmmmmmmmm think they may be illegal)

Regards

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Eur Ing John Colquhoun CEng MIET
Si Je Puis
Clarior Hinc Honos
Operations Manager - Telecommunications (Scotland) <img src="/forums/forum/i/expressions/face-icon-small-wink.gif" border="0">

Just had another thought (I know they are rare )

My wifes car is a Volkswagon and the headlights have alloy caps on them. Wonder if they are used to reduce pinpoint glare from the focal point of the bulb?

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Eur Ing John Colquhoun CEng MIET
Si Je Puis
Clarior Hinc Honos
Operations Manager - Telecommunications (Scotland) <img src="/forums/forum/i/expressions/face-icon-small-wink.gif" border="0">

oh yea, forgot about that design.

The main thing about headlight glare is people forgetting to adjust the tilt when they have four friends in the car and the weight in the back causes the headlights to tilt upwards. Mibbey a course on what the little adjuster next to the dashboard is for


Having the luminescence spread along the width of the bonnet instead of the two points would probably increase the near field lighting but the main issue everyone has is the far field of vision which will still require a narrower beam and therefore increased intensity - back to square one when you look into the light

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Eur Ing John Colquhoun CEng MIET
Si Je Puis
Clarior Hinc Honos
Operations Manager - Telecommunications (Scotland) <img src="/forums/forum/i/expressions/face-icon-small-wink.gif" border="0">

There seems to be at least three factors to headlight glare.
One, dimwits who drive with foglights all the time.
Two, people who have obviously tilted their lights up so they can drive on dip all the time and don't have to use main beam.
Three, maladjusted lights due to damage or corrosion of the mounts, which should be picked up by the MOT but for the woefully poor testing of beam alignment.

And the maximum wattage of the lamps rather than the little lumens are set out in the construction of vehicles requirements.

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Norman

By law a motor vehicle is allowed only 55 Watts consumption headlamp and stoplamp bulbs.

But some motorcycle shops will supply vastly powerful bulbs if you just ask, though they are illegal to use on the road.

I run a 128/55 Watt on one of my motorcycles and I have a friend who runs over 150/55 Watts on his.

This is needed as many drivers just can't be arsed to dip when they see a bike coming towards them. A quick Close Encounters Of The Third Kind blast with the "Arc Lamp" soon makes them hit the switch.

I've managed to light up the cat's eyes around a car over half a mile away before now.

A lot of bikes run illegal high power headlamps as a safety measure.

And in answer to the original question, the illunination source doesn't matter as much as the lens system employed, which controls the distribution of the light energy, and the frequency of the light source, due to the way the human eye's various visual systems operate.

Projector headlamps were invented in the 1920's and were soon replaced by the superiour Prismatic Lens System which we still have today. They have returned,however, as a fashion gimmic on small scooters and car fog lights. However they are still obstelete.

There is a lot of serious engineering and development put into some headlamp designs though some other seem to have been styled by art graduates than engineers.

Interesting article in this month's "New Electronics" here

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Andy Millar CEng MIET MCMI

http://www.linkedin.com/in/millarandy

Talking of headlamps, several weeks ago I was driving back home late at night and saw a truck coming the other way, with the front covered full of headlamps. I mean there were about a dozen of them protruding along the top and bottom rows not to mention the headlamps that actually came with the truck. As I remember it only the front two headlamps were on at the time.

As the truck came closer, I naturally pulled over to one side to let it pass by.

You know when you let someone through and they flash their headlamps to say thanks. Well this one went one better and flashed the whole set to say a big thanks.

It was like starring into one of those floodlights at a football match. Except this one was about 5 meters away.

Awesome!

Edited: 14 September 2007 at 05:37 PM by mbirdi

Somewhere in the depths of my storage space I have a copy of a British Standard for calibrating beam setters. It refers to placing the vehicle 8m (was 25') from a vertical wall and setting the root of the angled part of the beam directly ahead of the lamp and with the lower part of the beam at a height no higher than the centre of the lamp.

It is rare to find a garage that will set lamp properly. Normally, the only concern is to set the lamps low enough to pass the legal (1050mm?? Was 3'6".) dazzle limit when on dip and set the angled part far enough left: MoT pass. Whether the driver can actually see where he is going seems irrelevant.

I have just bought another car. I was out last night in the supermarket car park with my tape measure and my piece of chalk. Sorted!


(I still maintain that proper headlamps are round, 180mm in diameter and are marked 'Made in France'.)

Headlights are fitted to cars vans and HGV and motorbikes, when you take into account the range of sizes from micro minis to big 4x4 a headlamp tester has to test all, you can only check beam angle ie pointing downwards and dip down and n/s if it falls within the box it passes, and of course roads bend raise and fall so you could find some ones beam directly at you. And if your in a small car that four wheel jeep will have its headlights at your eye level. Trouble with headlight
adjusters most drivers dont have a clue what to do with them ,ie does winding it down put lights down or up?

As a frequent traveller to France with my car, I am reminded how inefficient its headlights are rendered by the obligatory masking of the lens downswept-beam portion.
Its probably as I imagine driving those staff cars seen in wartime movies, where only a small slot was cut out of headlight full masks. I'm sure I've seen British cars (probably of German manufacture) where operating a simple mechanical lever at the rear of each lamp housing was all that was needed to convert the headlights to full brightness and correctly-dipping mode for continental driving. Or was that another of my wishful dreams? ;-)

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Alan Kay, CEng MIEE

The Road Vehicle Lighting Regulations 1989 specify that vehicles first used from 1986 onward are required to have lamps bearing appropriate approval marks. I'm not familiar with the contents of the applicable standards, so the 55W limitation might apply to headlights on newer vehicles.

But certainly as far as pre-1986 vehicles are concerned, the only requirement listed in the regulations is the headlights be a minimum of 30 watts. No maximum is specified (see schedules 4 & 5).

For stop lights, the permitted range of power rating is 15 to 36 watts for 1971 vehicles onward, and no specific requirement for older cars (see schedule 12).

http://www.opsi.gov.uk/si/si19...19891796_en_1.htm#tcon

Edited: 13 December 2008 at 10:03 PM by Paul1966

sure i've heard of these too

In reply to the original post. I think the idea that a distributed light source would be less dazzling for the same illumination is a good one. That seems to be the experience in football grounds where lighting gantries across the whole length of the stands has, in recent years, replaced the old floodlight pylons.

On my first visit to this site I made the mistake of putting headlamp glare into Emerging Technology.
If I knew how to move the topic here life would be simple. If you look you will see a good cheap way to avoid headlamp dazzle.Maybe I should run through it all again here.